Enhancement of the spin Hall voltage in a reverse-biased planar pn-junction

TL;DR

This paper demonstrates that reverse-biasing a pn-junction in GaAs/AlGaAs microdevices significantly amplifies the spin Hall voltage by expanding the depletion zone, enhancing the local spin signal by over tenfold.

Contribution

It introduces a method to locally amplify the spin Hall voltage using reverse bias in a pn-junction, revealing new control over spin transport signals.

Findings

Depletion zone can be expanded by at least 10 μm at low temperature.

Spin Hall signals increase by more than an order of magnitude in the depleted regime.

pn-bias influences both local drift field and carrier density, affecting spin transport.

Abstract

We report an experimental demonstration of a local amplification of the spin Hall voltage using an expanding depletion zone at a pn-junction in GaAs/AlGaAs Hall-bar microdevices. It is demonstrated that the depletion zone can be spatially expanded by applying reverse bias by at least 10~$\mu$m at low temperature. In the depleted regime, the spin Hall signals reached more than one order of magnitude higher values than in the normal regime at the same electrical current flowing through the micro-device. It is shown that the pn-bias has two distinct effects on the detected spin Hall signal. It controls the local drift field at the Hall cross which is highly non-linear in the pn-bias due to the shift of the depletion front. Simultaneously, it produces a change in the spin-transport parameters due to the non-linear change in the carrier density at the Hall cross with the pn-bias.